There are several medical indications for which vascular occlusion is an appropriate treatment including, for example, for rerouting blood to a different part of a patient's body, to reduce or halt supply of blood to a tumor or other growth, to reduce the supply of blood to an organ or area of a patient's body prior to a medical procedure or treatment, to reduce pressure on a fistula, weakened or leaking blood vessel, and so on.
Conventionally, vascular occlusion was effected by surgically closing, or ligating, the blood vessel. This required an open surgery procedure with consequential risks and complications.
More recently, vascular occlusion has been effected by the endoluminal implantation into a patient of one or more implantable medical devices. A well-known device is in the form of a wire coil which can be implanted in a patient's vasculature and which achieves occlusion by promoting embolization of blood. Typically, several such coils are implanted one adjacent the other until the medical practitioner is satisfied that adequate occlusion has been achieved. In this regard, it can take time to attain adequate occlusion and also the length of the occluding barrier, that is the overall length of the implanted coils, will vary and can be significant. In some cases, there may not be sufficient room in a vessel to accommodate a long length of coils without adversely affecting other parts of the patient's vasculature, such as side branches bifurcations and so on.
It is also known to effect occlusion by administration of thrombogenic agent into a patient, for instance by injection of the agent between two spaced balloons inflated in a patient's vessel. The balloons are removed following the generation of the blood clot, thereby to create occlusion without leaving in the patient's body any foreign device. The procedure can generate an occluding barrier of set length, thereby making the occlusion barrier suitable for complex vessel anatomies. However, occlusions of this nature can be liable to recanalization; that is, to leakage through the occluding barrier and reopening of the vessel.
Other types of implantable occluders seek to mitigate the above drawbacks but can still be prone to migration, recanalization and migration following implantation.